MEMS devices are utilized in a variety of environments. Under shock conditions MEMS devices will travel beyond normal operating range and for a MEMS element mounted on a substrate, the MEMS element may contact the substrate. The substrate could be a complementary metal-oxide-semiconductor (CMOS) substrate. Over-travel stops are typically formed on the uppermost base layer to prevent damage to sensitive electrodes during large shock. However under low shock conditions the MEMS element can get stuck on an over-travel stop rendering the MEMS inoperable. This failure is commonly referred to as stiction.
Conventionally over-travel stops are made from non-conductive materials, such as silicon nitride (SixNy) and silicon dioxide (SiO2). Over-travel stops made of non-conductive materials can charge during operation creating an undesirable electrostatic force on a MEMS element leading to offset. There is a need to provide systems that overcome charge induced offset while preventing damage under large shock and preventing stiction under low shock conditions. The present invention addresses such a need.